Re: feature-request / doc-actualization (right-margin)

[Michael Käppler]

Hi Maximilian,
> 1) The code in scm/page.scm is able to test whether left-margin and/or
> right-margin was specified by the user in the \paper block (if this
> isn't the case, the value is #f). However, the same doesn't seem to be
> true for line-width because this variable _always_ has a value (i.e.,
> it cannot be undefined like the other two). Thus I cannot check
> whether both the left+right margins *and* the line-width were
> specified by the user. As Werner pointed out, we should print a
> warning in this case and discard one of the values. BTW, how can I
> find out which of the values was specified last in the .ly file so
> that that's the one taken into account?
>   
I don't think it's possible to determine which variable in a \paper {} 
block was set first. But in my opinion that's not necessary at all, 
because it's no problem to discard the same value every time this occurs 
(maybe, e.g. if left+right margins are set and line-width too, 
line-width can discarded), if you print a warning. However, I would 
print a warning just if the values are incompatible to each other what 
can be checked easily.
> When adding the line
>
>    line-width = 10 \cm
>
> to the \paper block it still kinda "works" (the line-width value is
> simply discarded so that the margins are as specified). Interestingly,
> however, the value of line-width still has an effect on the *spacing*
> of the notes. Namely, the notes are spaced as if the line-width were
> truly 10cm but then the line gets stretched to account for the margin
> values. How can this be avoided? Or is it even a feature rather than a
> bug? (I can imagine that some users might want to make use of this to
> achieve tighter or wider spacing, although I'm not sure that's a good
> idea.)
>   
This is because line-spacing is done earlier than page-spacing - Lily 
needs a value for line-width when doing horizontal spacing. Therefore 
line-width isn't really discarded - but later in page.scm it is 
overwritten, so you can't see it in the page layout.
What I wasn't unable to figure out is at which time line-width is 
calculated if you don't set it explicitly. And, much more confusing, I 
don't see any procedures in C++ that actually check the line-width. A 
"grep -R line-width *" isn't very informative.
Any ideas?

Regards,
Michael